<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    *{
      margin: 0;
      padding: 0;
    }
    .father{
      width: 400px;
      height: 400px;
      background-color: brown;
      /* overflow: hidden; */
      /* border: 1px solid transparent; */
      /* padding-top: 20px;
      box-sizing: border-box; */

    }
    .father::before {
      content: "";
      display: table;
      height: 0;
    }
    .d1 {
      width: 100px;
      height: 100px;
      background-color:aquamarine;
      margin-top: 20px;
    }
  </style>
</head>
<body>
  <div class="father">
    <!-- <table></table> -->
    <div class="d1"></div>
    <div class="d2"></div>
  </div>
</body>
</html>